The present invention relates to a printing press with a plate making unit for performing plate making for a plate mounted on the plate cylinder of a printing unit.
Generally, when performing plate making for a plate, it is required to increase the efficiency of plate making operation and to eliminate the space where a plate making unit is to be installed. Hence, in recent years, a plate making unit independent of the printing press is not provided, but a plate making unit added to the printing press itself performs plate making directly on the printing press. More specifically, a plate before plate making is mounted on a plate cylinder in a printing unit, and the plate making unit is moved to abut its head against the plate cylinder. Subsequently, the plate cylinder is rotated, and simultaneously the head is moved in the axial direction of the plate cylinder, thereby performing plate making for the plate. When the plate is to be supplied/removed or maintenance is to be performed, the plate making unit is separated from the printing unit.
In the conventional printing press described above, the plate making unit is temporarily moved at a position separate from the printing unit in order to perform maintenance or the like, and is moved at a position where plate making is to be performed again after maintenance completion. When the plate making unit is moved after maintenance completion, the position of the head greatly depends on the positioning precision of the plate making unit with respect to the printing unit. Poor head positioning precision greatly affects plate making precision and printing precision.
When the plate making unit is provided to each of a plurality of printing units, poor positioning precision affects the register accuracy of each ink color. In this case, an operator must perform the complicated, skilled operation of adjusting the positions of the plate cylinders in the printing units for the purpose of registration. This increases the load of the operator and requires the long preparation time, thereby reducing the productivity. Even if the plate making unit is correctly positioned to the printing unit, the position error of the head for the plate making unit poses the same problem.
It is an object of the present invention to provide a printing press in which the plate making precision and printing precision are improved.
In order to achieve the above object, according to the present invention, there is provided a printing press comprising a plate cylinder which is rotatably supported by a frame and has an outer surface on which a plate is mounted, a plate making unit supported to be movable between an operative position where plate making is performed and a wait position to escape from the operative position to perform plate making for the plate, the plate making unit having an exposure unit with a head which irradiates the plate with a laser beam to print an image on the plate, and a support mechanism for supporting the exposure unit to be movable in an axial direction of the plate cylinder, and detection means for detecting a position of the exposure unit with reference to the frame.
FIG. 1 is a side view schematically showing a printing press according to an embodiment of the present invention;
FIG. 2A is a partially sectional side view of the main part of the printing press of FIG. 1, and FIG. 2B is a view seen in the direction of arrow I of FIG. 2A;
FIG. 3 is a plan view of the main part of the printing press shown in FIG. 1;
FIG. 4A is a perspective view of a printing unit the opening of which is closed with the plate making unit shown in FIG. 2A, and FIG. 4B is a perspective view of the printing unit the opening of which is open;
FIG. 5 is a perspective view of the printing unit from which a cover and the plate making unit are removed;
FIG. 6 is a front view of the plate making unit shown in FIG. 2A;
FIG. 7A is a partially cutaway side view of the plate making unit shown in FIG. 2A, and FIG. 7B is a view seen in the direction of arrow II of FIG. 7A;
FIG. 8 is a perspective view of the base unit shown in FIG. 7A;
FIG. 9 is a longitudinal sectional view of the base unit shown in FIG. 8;
FIG. 10A is a side view of the plate making unit shown in FIG. 2A, FIG. 10B is a view seen in the direction of arrow III of FIG. 10A, and FIG. 10C is an enlarged view of a portion IV of FIG. 10B;
FIG. 11 is a perspective view, seen from the rear side, of the guide structure of an exposure unit;
FIG. 12 is a perspective view, seen from the front side, of the guide structure of the exposure unit;
FIGS. 13A and 13B are a partially cutaway plan view and partially cutaway side view, respectively, of the position adjusting mechanism of the exposure unit;
FIG. 14 is an enlarged perspective view of the position adjusting mechanism of the exposure unit; and
FIGS. 15A and 15B are front views showing the position adjusting mechanism of the exposure unit according to other examples.